Cold rolling process for rolling hard metal or metal alloys

ABSTRACT

The present invention relates to a cold rolling process for rolling hard metal or metal alloys, comprising applying an effective amount of an oil composition comprising a base stock oil and, based on the total weight of the composition, from 1 to 80% by weight of di(2-ethylhexyl)adipate. Example of hard base metals include steel and nickel.

The present invention relates to a cold rolling process for rolling hardmetal or metal alloys.

The stainless steel rolling industry expresses the need to maximize theefficiency of their rolled metal manufacturing process. In generalterms, this means that they wish to operate at higher rolling speeds andto produce more marketable products per operating shift. Additionally,they also wish to minimize the number of passes through the mill takento achieve a given level of reduction. Both these routes require thatquality and surface finish be not compromised. Also, there is a wish toroll harder materials, such as special steels (e.g. molybdenum steel)and/or allow higher reduction ratios.

The invention thus provides a cold rolling process for for high-speedcold rolling mills that affords the following customer benefits:

-   -   lower rolling and reduced mill power (this allowing rolling        harder material and/or allow higher reduction ratios);    -   allow one or two pass(es) reduction versus conventional oil        lubrication;    -   improved rolled surface finish (especially on ferritic and        austenitic steels), e.g. brightness improvement.

The invention is effective on any type of cold rolling, be it reversibleor not, of the Sendzimir type (e.g. 1-2, 1-2-3, 1-2-3-4), or of Z-hightype (e.g. 2-high, 4-high, 6-high), be it a reversible mill, a tandemmill, etc.

Especially, the invention exhibits high reduction and rollingcapabilities while providing an excellent strip surface finish whenrolling at high speed. The invention is also suited to Z-high rollingmill technology where high reduction ratio at low speed is obtained.

Masuda et al, in “Effect of rolling oil additives on Heat Scratchgeneration—a study on rolling oils for cold rolling of stainlesssteels”, Journal of the JSTP, vol.28, No. 316 (1987-5) discloses an oilcomposition comprising various esters, which are selected from the groupconsisting in 2-ethylhexyl stearate, di(2-ethylhexyl) phthalate,trimethylolpropane caprate, dimer-acid methyl ester and lard methylester.

The prior art does not teach or even suggest the instant invention.

Thus, the invention provides a cold rolling process for rolling hardmetal or metal alloys, comprising applying an effective amount of an oilcomposition comprising a base stock oil and, based on the total weightof the composition, from 1 to 80%, preferably from 1 to 30% by weight,of di(2-ethylhexyl)adipate.

According to one embodiment, the hard metal or metal alloys are selectedin the group consisting of steel and stainless steel. The steels andstainless steels to which the invention applies are any steel, includingvery hard steels.

According to a further embodiment the hard metal is a non-ferrous metal,like nickel or lead.

According to a further embodiment, the hard metal or metal alloys areselected from nickel and Invar®, which is a trademark of Imply SA fornickel-iron alloys.

According to a further embodiment, the oil composition further comprisesan alkyl alkylate ester, in which the alkyl comprises 2 to 8 carbonatoms and the alkylate comprises 14 to 24 carbon atoms, preferablyn-butyl, iso-butyl, or tert-butyl stearate, and where the weight ratiodi(2-ethylhexyl)adipate:alkyl alkylate ester is from 1:1 to 20:1.

According to a further embodiment, wherein the oil composition furthercomprises a fatty alcohol having from 10 to 20 carbon atoms, preferablyfrom 12 to 18 carbon atoms. Altough the fatty alcohol can be linear orbranched, linear alcohols are preferred.

According to a preferred embodiment, the fatty alcohol is laurylalcohol.

When used with steel or stainless steel, the cold rolling oilcomposition comprising a base stock oil and, based on the total weightof the composition, from 1 to 80% of di(2-ethylhexyl)adipate, exhibitsthe following roll force versus % reduction at a roll speed of 300 m/minsuch as:RF<200R−5900

where RF is the Roll Force expressed in tons/m and R is reductionexpressed in %, and where RF is >500 tons/m.

When used with steel or stainless steel, the cold rolling oilcomposition comprising a base stock oil and, based on the total weightof the composition, from 1 to 80% of di(2-ethylhexyl) adipate, exhibitsthe following roll force versus % reduction at a roll speed of 700 m/minsuch as:RF<80R−1550

where RF is the Roll Force expressed in tons/m and R is reductionexpressed in %, and where RF is >400 tons/m.

The invention is now disclosed in more details in the followingspecification, and in reference to the drawings in which:

FIG. 1 is a graph showing the rolling force versus the reduction, at 300m/min, when using a prior art process and the process of the invention,evidencing the influence of the oil composition on reduction capacity;

FIG. 2 is a graph showing the rolling force versus the reduction, at 700m/min, when using a prior art process and the process of the invention,evidencing the influence of the oil composition on reduction capacity.

The applied oil compositions are neat oils.

The base stock oil is any oil typically used in the field of coldrolling. It can be paraffinic or naphthenic, hydrocracked or not.

Paraffinic base oils are made from crude oils that have relatively highalkane contents (high paraffin and isoparaffin contents). Typical crudesare from the Middle East, North Sea, US mid-continent. The manufacturingprocess requires aromatics removal (usually by solvent extraction) anddewaxing. Paraffinic base oils are characterized by their goodviscosity/temperature characteristics, i.e. high viscosity index,adequate low-temperature properties and good stability. They are oftenreferred to as solvent neutrals, where solvent means that the base oilhas been solvent-refined and neutral means that the oil is of neutralpH. An alternative designation is high viscosity index (HVI) base oil.They are available in full range of viscosities, from light spindle oilsto viscous brightstock.

Naphthenic base oils have a naturally low pour point, are wax-free andhave excellent solvent power. Solvent extraction and hydrotreatment canbe used to reduce the polycyclic aromatic content.

A preferred base oil is an hydrotreated paraffinic neutral.

The base oil typically has a viscosity from 5 to 40 cSt at 40° C. andpreferably from 7 to 16 cSt at 40° C. Viscosity can be adjusted by usinga viscosity adjuster (such as kerosene type petroleum cut), if needed.

Preferred base oils are those with compounds having a carbon contentbetween 20 and 25, preferably between 22 and 24.

Also preferred are base oils having an aromatic content equal or smallerthan 5% by weight.

The flash point of the base oil is preferably greater than 150° C., andtypically is 154° C.

The oil may comprise classical additives, such as surfactants, couplingagents or cosurfactants, friction reducing agents, lubricity agents,corrosion inhibitors or anti-oxidants, extreme-pressure and anti-wearagents, anti-foaming agents, anti-rust agents.

Examples of anti-foaming agents are silicone based, especiallypolydimethylsiloxane.

Examples of corrosion inhibitors are hindered phenols and zincdialkyldithiophosphates (ZDDP).

Examples of extreme-pressure and anti-wear agents are dilaurylphosphate, didodecyl phosphite, trialkylphosphate such astri(2-ethylhexyl)phosphate, tricresylphosphate (TCP), zinc dialkyl(ordiaryl)dithiophosphates (ZDDP), phospho-sulphurized fatty oils, zincdialkyldithiocarbamate), mercaptobenzothiazole, sulphurized fatty oils,sulphurized terpenes, sulphurized oleic acid, alkyl and arylpolysulphides, sulphurized sperm oil, sulphurized mineral oil, sulphurchloride treated fatty oils, chlornaphta xanthate, cetyl chloride,chlorinated paraffinic oils, chlorinated paraffin wax sulphides,chlorinated paraffin wax, and zinc dialkyl(or diaryl)dithiophosphates(ZDDP), tricresylphosphate (TCP), trixylylphosphate (TXP), dilaurylphosphate, respectively.

Examples of corrosion inhibitors or anti-oxidants are radical scavengerssuch as phenolic antioxidants (sterically hindered), aminicantioxidants, organo-copper salts, hydroperoxides decomposers, butylatedhydroxytoluene.

Examples of anti-rust agents are amine derivative of alkenyl succinicanhydride.

Examples of friction reducing agents or lubricity agents are fattyalcohols having a carbon number in the range from 12 to 18, fatty estershaving a carbon number in the range from 12 to 18, like glycerolmonooleate.

Further elements on base oils and additives can be found in “ChemistryAnd Technology Of Lubricants”, R. M. Mortier and S. T. Orszulik, VCHPublishers, Inc, First published in 1992.

The cold rolling process is the classical process.

The work roll surface does not need to be coated.

The oil temperature is generally maintained at a temperature below 70°C., preferably below 50° C. The process can be carried out on anyrolling mill, such as of the Sendzimir type or of the Z-high type, intandem, etc. The instant oil composition allows a significant reductionof the number of passes. With conventional prior art oils, the number ofpasses was typically 10. The oil composition of the invention allowslowering this number to 8 passes, which is a significant gain.

The following example illustrate the invention without limiting it. Allparts and ratios are given by weight.

EXAMPLE

The following composition is prepared:

TABLE 1 Ingredients Content (wt %) Base oil (paraffinic, 9 cSt at 40°C.) 88.75 Butylated hydroxytoluene 0.20 tri(2-ethylhexyl)phosphate 1.00Amine derivative of alkenyl succinic anhydride 0.05 di(2-ethylhexyl)adipate 10.00

An oil composition as used in a process of the prior art is alsoprepared. It comprises the following ingredients:

TABLE 2 Ingredients Content (wt %) Base oil (paraffinic, 9 cSt at 40°C.) 97.40 Butylated hydroxytoluene 0.10 tri(2-ethylhexyl)phosphate 0.50Lauryl alcohol 1.00 n-butyl stearate ester 1.00

The process of the invention and of the process of the prior art aretested according to the following method.

The test mill is a non-reversing single stand 2-high rolling mill withcoiler and decoiler designed for 30 mm wide sheets, which can take up to0.6 mm thick strips of around 1,000 m length. The rolls have a width of100 mm and a diameter of 95 mm, and the composition of their steel isZBSVCD8-3 (which is used for certain Sendzimir mills).

The first run is to evaluate the reduction capacity in one pass, at aconstant speed of 300 m/mn. The curve “rolling force” as a function ofthe reduction rate is recorded when increasing reduction levels. Therolled strip composition is a bright annealed ferritic stainless steelFS30 (Z8 C17, 17% chromium) having a strip thickness of 0.4 mm.

The results of the run are depicted in FIG. 1.

The line of the process of the invention corresponds to the equation

RF=200R−5900, where RF is the Rolling Force expressed in tons/m and R isthe reduction expressed in % (where RF is >500 tons/m).

The second run is to evaluate the reduction capacity in one pass, at aconstant speed of 700 m/mn. The results are depicted in FIG. 2, in whicha prior art process and the process of the invention are compared. Theline of the process of the invention corresponds to the equation

RF=80R−1550, where RF is the Rolling Force expressed in tons/m and R isthe reduction expressed in % (where RF is >400 tons/m).

The finish of the products has been determined and has been foundexcellent with the process of the invention.

From the figures it is quite apparent that:

-   -   in the process of the invention, at low rolling speed (300 m/mn)        , as well as at high rolling speed (700 m/min), the reduction        capability is at least equivalent to that of the conventional        process; and    -   the higher the reduction rate, the better the results obtained        with the process of the invention as compared with results        obtained with the process of the prior art.

In addition, the improvement provided by the process of the invention isobtained without impairing the surface finish of the rolled strip.

Additionally, the process of the invention was used to roll pure nickel.The applied oil composition was that of Table 1.

The roll conditions were as follows

-   -   rolling speed: 300 m/min;    -   roll width: 15 mm    -   initial thickness: 0.52 mm

With a reduction force of 300 tons/m, the reduction rate was 46%.

In the same conditions, pure nickel was rolled with the oil compositionof table 2.

With a reduction force of 300 tons/m, the reduction rate was only 42%.

1. In the cold rolling process of hard metal and of hard metal alloysusing a rolling oil composition, the improvement comprising using an oilcomposition comprising a base stock oil and, based on the total weightof the composition, from 1 to 80% by weight of di(2-ethylhexyl)adipate.2. The improvement according to, claim 1 wherein the oil compositionfurther comprises an alkyl alkylate ester, in which the alkyl comprises2 to 8 carbon atoms and the alkylate comprises 14 to 24 carbon atoms,and where the weight ratio di(2-ethylhexyl)adipate:alkyl alkylate esteris from 1:1 to 20:1.
 3. The improvement according to claim 2, in whereinthe alkyl alkylate ester is n-butyl, iso-butyl, or tert-butyl stearate.4. The improvement according to claim 2, wherein the oil compositionfurther comprises a fatty alcohol having from 10 to 20 carbon atoms,preferably from 12 to 18 carbon atoms.
 5. The improvement according toclaim 4, wherein the fatty alcohol is lauryl alcohol.
 6. The improvementaccording to claim 2, in which the base stock oil has a viscositycomprised between 5 and 40 cSt at 40° C., and preferably between 7 and16 cSt at 40° C.
 7. The improvement according to claim 6, in which thebase stock oil comprises compounds having a carbon content between 20and 25, preferably between 22 and
 24. 8. The improvement according toclaim 7, in which the base stock oil has an aromatic content equal orsmaller than 5% by weight.
 9. The improvement according to claim 8, inwhich the base stock oil has a flash point greater than 150° C.
 10. Theimprovement according to claim 2, wherein the oil composition comprises,based on the total weight of the composition, from 1 to 30% by weight ofdi(2-ethylhexyl)adipate.
 11. The improvement according to claim 1 of 10,wherein the hard metal or metal alloys are selected in the groupconsisting of steel and stainless steel.
 12. The improvement accordingto claim 1 or 10, wherein the hard metal is a non-ferrous metal.
 13. Theimprovement according to claim 1 or 10, wherein the hard metal or metalalloys are selected in the group consisting of nickel and nickel-ironalloys.